use proconio::{input, marker::Chars};

fn main() {
	input! {
		n: usize,
		s: Chars,
	}
	
	let mut ans = 0_i128;
	for i1 in 0 .. n {
		for i2 in i1 + 1 .. n {
			if s[i1] == s[i2] {
				continue;
			}
			for i3 in i2 + 1 .. n {
				if s[i1] != s[i3] {
					continue;
				}
				for i4 in i3 + 1 .. n {
					if s[i1] == s[i4] || s[i2] == s[i4] {
						continue;
					}
					for i5 in i4 + 1 .. n {
						if s[i1] == s[i5] || s[i2] == s[i5] || s[i4] == s[i5] {
							continue;
						}
						ans += 1;
					}
				}
			}
		}
	}
	
	println!("{ans}");
}